The milestone, he said, means Facebook has joined the pantheon of things that help connect humans.

"Chairs, doorbells, airplanes, bridges, games," he wrote. "These are all things that connect us. And now Facebook is a part of this tradition of things that connect us too."

The Los Angeles Times takes a look at what this means for Facebook's business. Since the company went public, it's been buffeted by doubt and questions on whether its worth as much as was estimated during its initial public offering.

The problem Facebook faces, says the Times, is that it's had explosive growth leading up to the 1 billion number. But from here on out, the pace will almost certainly be slower.

The Times reports:

"The next billion will be a lot tougher than the first. One big reason: A third of the world's population can't access Facebook. The Chinese government has blocked access to the website since 2009, although many still scale the "great firewall" to use it.

"It's a big gap for Facebook. The Chinese are avid users of social networks. Zuckerberg has said that Facebook has no immediate plans to enter China."